Lambert denies the allegations and plans to fight them in court, his attorney William Sullivan said during a pre-trial hearing.

Prosecutors allege Lambert, former co-president of a Maryland-based shipping company Transport Logistics International (TLI), bribed a Russian energy official through a series of shell companies in Cyprus, Latvia and Switzerland in exchange for contracts to ship nuclear fuel to U.S. utilities.

The U.S. Foreign Corrupt Practices Act makes it a crime for businesses to bribe overseas officials to win business.

TLI executives did not immediately respond to requests for comment.

For decades, Washington and Moscow had an agreement that converted uranium from Russia’s nuclear stockpiles to civilian grade fuel, which was shipped to the United States for use in civilian power plants.

The charges are the latest chapter in a sprawling federal investigation into corruption involved in Russia’s sale of uranium into the United States.

The uranium investigation drew increased public attention last year after an informant involved in the probe claimed to have evidence tying the former Obama Administration to Russian influence peddling, a charge former administration officials have denied.

In 2015, a Maryland judge sentenced the Russian official named in the case, Vadim Mikerin, a former director at state-owned Rosatom, to four years for laundering money connected to the bribes. Lambert’s former co-president Daren Condrey pleaded guilty to bribery and wire fraud charges in 2015 and is awaiting sentencing.